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  • 1.
    Adamopoulos, Stergios
    Aristotelian University, Greece.
    Flexural properties of black locust (Robinia pseudoacacia L.) small clear wood specimens in relation to the direction of load application2002In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 60, no 5, p. 325-327Article in journal (Refereed)
    Abstract [en]

    Values of pure moduli of elasticity (PMOE), experimental modulus of elasticity (MOE) in static bending and moduli of rigidity (GLR, GLT) were calculated in juvenile and mature black locust defect-free small wood specimens after loading in static bending alternately on true radial and tangential surfaces. For both juvenile and mature specimens, no significant differences (t-test, 95% probability level) were found between the radial and tangential moduli of elasticity and rigidity. Values of PMOE were found to be 27–32% higher than the corresponding values of MOE at the 15:1 span-to-depth ratio.

  • 2.
    Adamopoulos, Stergios
    Aristotelian University, Greece.
    Influence of hot-water extractives on radial and tangential shrinkage of black locust wood (Robinia pseudoacacia L.)2002In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 60, no 5, p. 377-378Article in journal (Refereed)
    Abstract [en]

    IntroductionRemoval of extractives increases the shrinkage and swelling of wood (Nearn 1955, Salamon and Kozak 1968, Cooper 1974, Taylor 1974). The effect of progressive extraction on the above properties has not been investigated much. In oak (Quercus conferta L.), a forest species rich in extractives, the shrinkage progressively increased with progressive extraction (Voulgaridis et al. 1980). In black locust (Robinia pseudoacacia L.), much of the main-stem volume is comprised of heartwood, characterized by the presence of dark yellow-brown extractives. While the extractives of black locust give the heartwood its distinctive color and decay resistance, they comprise only 6.2 to 8.3% of the dry weight of the main stem (Stringer 1992). Hot-water extractives range from 5.2 to 8.6% (Hart 1968, So et al. 1980). The present study was primarily undertaken to determine whether the progressive removal of hot-water extractives affects the radial and tangential shrinkage of black locust heartwood.

  • 3.
    Adamopoulos, Stergios
    et al.
    Georg-August-University Göttingen, Germany ; Technological Educational Institute of Larissa, Greece.
    Bastani, Alireza
    Georg-August-University Göttingen, Germany.
    Gascón-Garrido, Patricia
    Georg-August-University Göttingen, Germany.
    Militz, Holger
    Georg-August-University Göttingen, Germany.
    Mai, Carsten
    Georg-August-University Göttingen, Germany.
    Adhesive bonding of beech wood modified with a phenol formaldehyde compound2012In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 70, no 6, p. 897-901Article in journal (Refereed)
    Abstract [en]

    Untreated (controls) and phenol–formaldehyde (PF)-modified beech wood (10 and 25 % solid content) were glued with phenol resorcinol formaldehyde (PRF) and polyvinyl acetate (PVAc). Shear strength of PRF-bonded specimens was higher than that of PVAc-bonded ones under dry and wet conditions irrespective of the pre-treatment. Under dry conditions, only PVAc-bonded specimens exhibited reduction in shear strength due to PF-modification with 25 % PF concentration as compared to the controls. PF treated wood provided inferior bonding under wet conditions with the exception of 25 % PF concentration specimens glued with PRF adhesive. Modification with PF resulted in a decrease of adhesive penetration into the porous network of interconnected cells, especially at 25 % PF concentration.

  • 4.
    Adamopoulos, Stergios
    et al.
    Technological Educational Institute of Larissa, Greece.
    Milios, E.
    Democritus University of Thrace, Greece.
    Doganos, D.
    Democritus University of Thrace, Greece.
    Bistinas, I.
    Democritus University of Thrace, Greece.
    Ring width, latewood proportion and dry density in stems of Pinus brutia Ten2009In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 67, no 4, p. 471-477Article in journal (Refereed)
    Abstract [en]

    This study examined basic characteristics of stem wood produced in Pinus brutia Ten. reforestations in Northeastern Greece. Sixteen dominant trees growing at good and medium site qualities were felled at 14–22 years. Site quality classification was based on site quality surrogates and confirmed by using site index curves that were created for a neighbouring area. Discs were taken at three stem positions (base, middle, top) to study variations in ring width, latewood proportion and dry density. Generally, at both good and medium sites, ring width was found to increase towards the top of the stems while latewood proportion and dry density showed a negative relationship with stem height. Radial variability trends were similar at all heights, and at both sites, revealing a rapid increase for ring width in the first 3–6 annual rings followed by a decrease towards the bark, a gradual increase for latewood proportion and no specific change for dry density. Comparisons between wood material produced during the same growth period (2005–2001) showed statistically significant differences among sampling heights in all cases except for dry density in medium sites. At the base of the stems, mean ring width and dry density were significantly (P ≤0.05) higher at good sites (3.6 mm and 0.53 g/cm3) than at medium sites (3.0 mm and 0.50 g/cm3). However, the differences between the sites are of small magnitude and therefore have limited practical impact on wood processing. The availability of such data is useful in utilising small-dimension timber of brutia pine.

  • 5.
    Adamopoulos, Stergios
    et al.
    Technological Educational Institute of Larissa, Greece.
    Passialis, Costas
    Aristotle University, Greece.
    Relationship of the toughness and the modulus of elasticity in static bending of small clear spruce wood specimens2010In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 68, no 1, p. 109-111Article in journal (Refereed)
    Abstract [en]

    Unlike static bending, toughness is a mechanical property less commonly measured in clear wood. The paper presents results on the relationship of toughness and modulus of elasticity in static bending based on DIN standard tests on small, clear specimens of spruce, 2×2 cm2 in cross section.

  • 6.
    Adamopoulos, Stergios
    et al.
    Aristotle University, Greece.
    Voulgaridis, Elias
    Aristotle University, Greece.
    Dimensional changes of extracted and non-extracted small wood specimens of black locust (Robinia pseudoacacia L.)2003In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 61, no 4, p. 264-268Article in journal (Refereed)
    Abstract [en]

    From straight grained heartwood of black locust (Robinia pseudoacacia L.), specimens, 3 cm×3 cm in cross section and 0.5 mm (or 10 mm) in axial direction, were cut and used for the determination of dimensional changes and the rate of tangential swelling. Mean radial, tangential and axial shrinkage was 5.30%, 6.67% and 0.16%, respectively, while the coefficient of anisotropy was 1.26. Half of the specimens for the determination of the rate of tangential swelling were extracted for 48 h with distilled hot water. The tangential dimensional change and the time taken to attain half maximum swelling in air-dry and oven-dry specimens were assessed according to a common technique. Extractive removal resulted in an increase of the total magnitude of tangential swelling in both air-dry and oven-dry specimens. However, no significant differences in time taken to attain half maximum swelling between air-dry and oven-dry specimens were observed after extraction. The rate of tangential swelling was lower in air-dry specimens than in oven-dry specimens after 30 min of immersion in water when were non-extracted and after 5 min of immersion in water when were extracted. Extracted air-dry specimens had a greater rate of tangential swelling than non-extracted air-dry specimens and the same occurred for oven-dry specimens. Extraction resulted in a higher diffusion coefficient for air-dry specimens. The diffusion coefficient calculated for non-extracted air-dry specimens (0.901×10−4 cm2/min) showed that black locust is a difficult species to impregnate.

  • 7.
    Adamopoulos, Stergios
    et al.
    Aristotle University, Greece.
    Voulgaridis, Elias
    Aristotle University, Greece.
    Passialis, Costas
    Aristotle University, Greece.
    Variation of certain chemical properties within the stemwood of black locust (Robinia pseudoacacia L.)2005In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 63, no 5, p. 327-333Article in journal (Refereed)
    Abstract [en]

    From the bottom, middle, and top of three mature 35 to 37-year old black locust tree discs were cut and analysed to determine the variation within the stem of certain chemical properties. Hot-water extractive content was greater in heartwood than in sapwood, while the reverse occurred for the dichloromethane extractive content. Vertical stem analysis of hot-water extractives showed that they increased in heartwood but decreasedin sapwood from the bottom to the top of the stems while the reversal occurred for dichloromethane extractive content of sapwood. At the bottom and the middle of the stems, ash content was greater in sapwood than in heartwood, but at the top no difference was found between heartwood and sapwood. Ash content of both heartwood and sapwood was found to increase in the axial direction with respective values of 0.36% (bottom) and 0.76% (top) for heartwood and of 0.65% (bottom) and 0.76% (top) for sapwood. Ash analysis showed that considerable variations were found for the inorganic elements K and P being greater in sapwood than in heartwood. Heartwood was more acid than sapwood except for the top of the stems. Acidity mean values were found to increase from the bottom to the top of the stems in heartwood while they slightly decreased in sapwood. Total buffering capacity of heartwood was greater than that of sapwood and total buffering capacity of sapwood exhibited an inverse relationship to height. Very small acid equivalent values were determined only in sapwood. At the bottom, lignin content in heartwood (25.73%) was greater than in sapwood (18.13%). Lignin content of heartwood decreased from 25.73% at the bottom to 18.33% at the top, while that of sapwood was 18.13% at the bottom, 21.42% at the middle and 19.64% at the top.

  • 8.
    Adamopoulos, Stergios
    et al.
    Georg-August-University Goettingen, Germany ; Technological Educational Institute of Larissa, Greece.
    Xie, Yanjun
    Georg-August-University Goettingen, Germany.
    Militz, Holger
    Georg-August-University Goettingen, Germany.
    Distribution of blue stain in untreated and DMDHEU treated Scots pine sapwood panels after six years of outdoor weathering2011In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 69, no 2, p. 333-336Article in journal (Refereed)
    Abstract [en]

    Surface coating and bulk treatment of wood are two effective measures which can, individually or conjointly, protect exterior wood from deterioration. This paper reports on the blue stain attack in coated wood, untreated and modified with DMDHEU, after six years of natural exposure.

  • 9.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Sehlstedt-Persson, Margot
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Morén, Tom
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Development of a new rapid method for mould testing in a climate chamber: Preliminary tests2013In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 71, no 4, p. 451-461Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to develop fast, simple and robust solid wood mould testing methods for the use in small-scale laboratory tests. The objective was to investigate mould susceptibility of different wood materials within the batches. The proposed method is based on natural contamination of non-sterile surfaces in climates conducive to mould growth. For this purpose, a climate chamber with regulated temperature and relative humidity was used. The conditioning chamber was divided into upper and lower chamber by a thin layer of stainless steel placed horizontally above the fan to minimise air circulation to the sample in the upper compartment. Mould-infected samples from outdoor tests were used as a source of mould inocula, and test trials were conducted on Scots pine (Pinus sylvestris L.) sapwood. Samples were suspended from the top of the upper chamber, and the chamber was exposed to different temperature and humidity levels. Severe mould infestation was observed after 12-14 days of incubation. Visual mould rating was then performed. Regardless of some constraints, this test method was very simple, fast, and effective. More importantly, unlike other test methods, it closely models mould infestation as it would occur under natural condition.

  • 10.
    Ahmed, Sheikh Ali
    et al.
    Luleå University of Technology.
    Sehlstedt-Persson, Margot
    Luleå University of Technology.
    Morén, Tom
    Luleå University of Technology.
    Development of a new rapid method for mould testing in a climate chamber: preliminary tests2013In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 71, no 4, p. 451-461Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to develop fast, simple and robust solid wood mould testing methods for the use in small-scale laboratory tests. The objective was to investigate mould susceptibility of different wood materials within the batches. The proposed method is based on natural contamination of non-sterile surfaces in climates conducive to mould growth. For this purpose, a climate chamber with regulated temperature and relative humidity was used. The conditioning chamber was divided into upper and lower chamber by a thin layer of stainless steel placed horizontally above the fan to minimise air circulation to the sample in the upper compartment. Mould-infected samples from outdoor tests were used as a source of mould inocula, and test trials were conducted on Scots pine (Pinus sylvestris L.) sapwood. Samples were suspended from the top of the upper chamber, and the chamber was exposed to different temperature and humidity levels. Severe mould infestation was observed after 12–14 days of incubation. Visual mould rating was then performed. Regardless of some constraints, this test method was very simple, fast, and effective. More importantly, unlike other test methods, it closely models mould infestation as it would occur under natural condition.

  • 11.
    Alfredsen, Gry
    et al.
    Norwegian Forest and Landscape Institute, Norway.
    Bader, Thomas K.
    Vienna University of Technology, Austria.
    Dibdiakova, Janka
    Norwegian Forest and Landscape Institute, Norway.
    Filbakk, Tore
    Norwegian Forest and Landscape Institute, Norway.
    Bollmus, Susanne
    Georg-August-University of Göttingen, Germany.
    Hofstetter, Karin
    Vienna University of Technology, Austria.
    Thermogravimetric analysis for wood decay characterisation2012In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 70, no 4, p. 527-530Article in journal (Refereed)
    Abstract [en]

    The paper focuses on the use of thermogravimetric analysis (TGA) as a fast method for estimating the change of lignocellulosic materials during fungal degradation in laboratory trials. Traditionally, evaluations of durability tests are based on mass loss. However, to gain more knowledge of the reasons for differences in durability and strength between wooden materials, information on the chemical changes is needed. Pinus sylvestris sapwood was incubated with the brown rot fungusGloeophyllum trabeum and the white rot fungus Trametes versicolor. The TGA approach used was found to be reproducible between laboratories. The TGA method did not prove useful for wood deteriorated by white rot, but the TGA showed to be a convenient tool for fast estimation of lignocellulosic components both in sound wood and wood decayed by brown rot.

  • 12.
    Amiandamhen, Stephen
    et al.
    Stellenbosch University, South Africa.
    Montecuccoli, Zeno
    Stellenbosch University, South Africa.
    Meincken, Martina
    Stellenbosch University, South Africa.
    Barbu, Marius
    Stellenbosch University, South Africa.
    Tyhoda, Luvuyo
    Stellenbosch University, South Africa.
    Phosphate bonded wood composite products from invasive Acacia trees occurring on the Cape Coastal plains of South Africa2018In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 76, no 2, p. 437-444Article in journal (Refereed)
    Abstract [en]

    The feasibility of manufacturing phosphatebonded wood composite board products from four locallyoccurring invasive acacia tree species (Acacia cyclops, A.saligna, A. mearnsii and A. longifolia) was studied usinga formulated magnesium oxide (MgO) and monopotassiumphosphate (KH2PO4) binder system. The optimizationfor the manufacturing process was studied using a centralcomposite statistical design, whereupon the following factorswere considered, i.e. KH2PO4:MgO ratio, the fly ashcontent as partial replacement for the binder and the woodcontent as a ratio of wood to the total inorganic content.A fitted response surface plot was used to show the effectof the main factors and their interactions on the measuredboard properties. A response surface model was developedto predict the parameters leading to the best board properties.All physical properties evaluated met or exceededthe minimum requirements for low density particleboards.The results showed that the variables considered have significanteffects on the physical properties of the boards.The optimum composite manufacturing process for makingdurable products within the scope of the studied specieswas found to be a KH2PO4/MgO ratio of 1.66, an ashcontent of 2.7% and a wood/inorganic ratio of 0.96 for theselected wood species.

  • 13.
    Antti, Lena
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Microwave drying of pine and spruce1995In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 53, no 5, p. 333-338Article in journal (Refereed)
    Abstract [en]

    microwave energy consumption from 365 to 760 kWh/m 3. Internal wood temperatures up to 140°C were used. Internal vapour pressure in the wood could rise to about 20 kPa without checking. Maximal drying rates of 0.20 to 0.45% moisture content per minute are possible to obtain when drying above fiber saturation (fsp). Below fsp the feasible drying rates ranged from 0.10 to 0.20% moisture content per minute. Spruce dried approximately 1.6 times faster than pine. No conditioning of the wood was necessary since the wood was free of stresses. The wood was free of checks but colour changes occured in the interior of some specimens.

  • 14.
    Axelsson, B.O.M.
    Luleå tekniska universitet.
    Lateral cutting force during machining of wood due to momentary disturbances in the wood structure and degree of wear of the cutting tool1994In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 52, no 3, p. 198-204Article in journal (Refereed)
    Abstract [en]

    The paper presents a study of the effect of momentary disturbances due to variations in wood structure on the lateral cutting force. Density, shape and fibre-direction of the disturbances, and the degree of wear of the cutting tool are taken into consideration. The paper shows that high density gradients result in high lateral forces. The highest momentary lateral force noted has a value of approximately 40 N. The geometrical shape of the cutting tool in terms of degree of wear has a big impact on the lateral force. The work indicates a potential to increase the cutting performance by a more accurate supervision of the condition of the cutting tools.

  • 15.
    Axelsson, B.O.M.
    et al.
    Luleå tekniska universitet.
    Grundberg, Stig
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    The use of gray scale images when evaluating disturbances in cutting force due to changes in wood structure and tool shape1991In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 49, no 12Article in journal (Refereed)
    Abstract [en]

    A method is presented for studying the effect of momentary disturbances due to variations in wood structure on the cutting force near the cutting edge. Force and density measurements are converted to a gray scale image. This method is very effective as regards the evaluation of experimental tests

  • 16.
    Axelsson, B.O.M.
    et al.
    Luleå tekniska universitet.
    Lundberg, Staffan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Studies of the main cutting force at and near a cutting edge1993In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 51, no 1, p. 43-48Article in journal (Refereed)
    Abstract [en]

    The present work is a study of how various parameters affect the cutting forces at, and near a cutting edge when cutting wood at full speed and with all cutting edges of the tool. Statistical methods from experimental results are used to develop a model

  • 17.
    Bastani, Alireza
    et al.
    Georg-August-University Göttingen, Germany.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Militz, Holger
    Georg-August-University Göttingen, Germany.
    Gross adhesive penetration in furfurylated, N-methylol melamine-modified and heat-treated wood examined by fluorescence microscopy2015In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 73, no 5, p. 635-642Article in journal (Refereed)
    Abstract [en]

    This study investigated the radial penetration of three conventional cold-set wood adhesives [emulsion polymer isocyanate (EPI), poly (vinyl acetate) (PVAc), one-component polyurethane (PU)] into various degrees of furfurylated and N-methylol melamine-modified (NMM) Scots pine, and heat-treated Scots pine and beech based on measurements of effective (EP) and maximum penetration (MP) from microscopic observations. EP of EPI adhesive decreased after modification with higher concentration of furfuryl alcohol while an improved penetration was recorded for PVAc into furfurylated wood. A deeper penetration was observed for all adhesives into wood treated with lower concentration of furfuryl alcohol. The EP of EPI and PU adhesives reduced after NMM treatment but it increased in the case of PVAc. In spite of reduction of EP of PU after NMM treatment, it represented a deeper penetration among all adhesives possibly due to its lower molecular weight. For Scots pine, increasing the treatment temperature improved EP of all adhesives while for beech, the EP of PU and PVAc increased largely in the case of samples treated at 195 °C. Visual analysis of fluorescence microscopy pictures provided more detailed information on modality of penetration. The results are useful for understanding the interaction among common adhesives and modified materials, and can be used in future research to explain the bonding behavior of modified wood.

  • 18.
    Bastani, Alireza
    et al.
    Georg-August-University Göttingen, Germany.
    Adamopoulos, Stergios
    Linnaeus University, Faculty of Technology, Department of Forestry and Wood Technology.
    Militz, Holger
    Georg-August-University Göttingen, Germany.
    Water uptake and wetting behaviour of furfurylated, N-methylol melamine modified and heat-treated wood2015In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 73, no 5, p. 627-634Article in journal (Refereed)
    Abstract [en]

    This study reports on the water uptake (WU) and wetting properties of different modified wood materials; furfurylated and N-methylol melamine (NMM) modified Scots pine, and heat-treated (Vacu3 method) Scots pine and beech. All modifications caused a substantial reduction in WU in the longitudinal, tangential and radial directions both after short (24 h) and long contact times (168, 336 h) with a saturated sponge. The water uptake coefficient (w t ) was reduced by approximately 71–89 % in furfurylated wood, with the higher weight percent gain (WPG) providing a slightly greater reduction. The reduction in WU was not found to depend on the NMM solid content. The NMM treatment had the maximum effect on the reduction of tangential w t by 80–84 % and was much smaller in the longitudinal direction (31–68 %). The treatment temperature of 195 °C gave lower WU values than treatment at 210 °C, and the only exception was the radial direction of Scots pine. The longitudinal w t of heat-treated beech represented the highest reduction by 81–89 %, while radial w t was less affected in both species. Sessile drop apparent contact angles for water and diidomethane and corresponding surface energies on planed tangential and radial wood surfaces revealed an increased hydrophobicity and reduced polarity of modified wood. Furfurylated and NMM modified tangential surfaces had a higher increase of apparent contact angles than the radial surfaces but this was not observed in the case of heat treatment. Heat-treated wood showed reduced wetting of surfaces only with water. Apparent contact angles did neither differ with treatment temperature nor with the NMM resin load. The disperse component of surface energy was slightly increased by 20 % maximum in modified wood, while the polar components showed a dramatic decrease by −30 to −90 % with no major differences among treatments and intensities, and between surfaces. The results provide a better understanding of the hygroscopic behaviour of modified wood, which might be useful to predict its adhesion with various polymers such as glues, coatings and paints.

  • 19.
    Bekhta, Pavlo
    et al.
    Ukrainian National Forestry University, Ukraine.
    Sedliacik, Jan
    Technical University in Zvolen, Slovakia.
    Jones, Dennis
    RISE - Research Institutes of Sweden, Built Environment, Building Technology.
    Effect of short-term thermomechanical densification of wood veneers on the properties of birch plywood2017In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736XArticle in journal (Refereed)
    Abstract [en]

    In this study, the physical and mechanical properties of plywood panels made from pre-compressed birch (Betula verrucosa Ehrh.) veneer were evaluated. Veneer sheets underwent short-term thermo-mechanical (STTM) compression at temperatures of 150 or 180 °C and at pressures of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 or 3.5 MPa for a period of 1 min prior to adhesive being applied and pressed into panels using phenol formaldehyde adhesive at 100 g/m2 spread rate; this was one-third less than the adhesive spread used for the control panels (150 g/m2). The pressing pressure was 1.0 MPa, which was almost half of the pressure used for the control panels (1.8 MPa); and pressing time was 3 min, also half of the pressing time used for the control panels (6 min). The results showed that surface roughness of compressed veneer, water absorption and thickness swelling of plywood panels made from compressed veneer were significantly improved. The shear strength values of plywood panels made from compressed birch veneer even with reduced adhesive spread were higher than those of plywood panels made from uncompressed veneer. The findings in this study indicated that compression of birch veneer could be considered as an alternative to produce more eco-friendly (owing to smaller adhesive spread) value-added material with enhanced properties.

  • 20.
    Bekhta, Pavlo
    et al.
    Ukranian National Forestry University.
    Sedliacik, Jan
    Technical University in Zvolen.
    Jones, Dennis
    DJ Timber Consultancy Ltd.
    Effect of short-term thermomechanical densification of wood veneers on the properties of birch plywood2018In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 76, no 2, p. 549-562Article in journal (Refereed)
    Abstract [en]

    In this study, the physical and mechanical properties of plywood panels made from pre-compressed birch (Betula verrucosa Ehrh.) veneer were evaluated. Veneer sheets underwent short-term thermo-mechanical (STTM) compression at temperatures of 150 or 180 ⁰C and at pressures of 0.5, 1.0, 1.5, 2.0, 2.5, 3.0 or 3.5 MPa for a period of 1 minute before being adhesive applied and pressed into panels using phenol formaldehyde adhesive at 100 g/m2 spread rate; this was one third less than the adhesive spread used for the control panels (150 g/m2). The pressing pressure was 1.0 MPa that was almost half of the pressure used for the control panels (1.8 MPa); and pressing time was 3 min, also half of the pressing time used for the control panels (6 min). The results showed that surface roughness of compressed veneer, water absorption and thickness swelling of plywood panels made from compressed veneer were significantly improved. The shear strength values of plywood panels made from compressed birch veneer even with reduced adhesive spread were higher than those of plywood panels made from un-compressed veneer. The findings in this study indicated that compression of birch veneer would be considered as an alternative to produce more eco-friendly (owing to smaller adhesive spread) value-added material with enhanced properties.

  • 21. Berglund, Anders
    et al.
    Johansson, Erik
    Förädling och processer (TRf).
    Skog, Johan
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Hållbar Samhällsbyggnad.
    Value optimized log rotation for strength graded boards using computed tomography2014In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 72, no 5, p. 635-642Article in journal (Refereed)
  • 22.
    Berglund, Anders
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Johansson, Erik
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Skog, Johan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Value optimized log rotation for strength graded boards using computed tomography2014In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 72, no 5, p. 635-642Article in journal (Refereed)
    Abstract [en]

    A possible application for an industrial computed tomography scanner in a sawmill is finding an optimal rotational position of logs with respect to knots and outer shape. Since a computed tomography scanner is a great investment, it is important to investigate potential profitability of such an investment for different production strategies. The objective of this study was to investigate the potential value increase of the sawn timber of Norway spruce (Picea abies (L.) Karst.) by rotating logs to their optimum position prior to sawing compared with sawing all logs in horns down position. The production strategy evaluated by log breakdown simulation in this case study was to produce strength graded timber of the center boards, while the side boards were appearance graded. This case study showed an average value increase with respect to the value of center boards, side boards and chips of 11 %.

  • 23.
    Blomberg, Jonas
    et al.
    Dalarna University, School of Technology and Business Studies, Wood Technology.
    Persson, Bengt
    Dalarna University, School of Technology and Business Studies, Wood Technology.
    An algorithm for comparing density in CT-images taken before and after compression of Pinus sylvestris2005In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 63, no 1, p. 23-29Article in journal (Refereed)
    Abstract [en]

    Ten plain-sawn boards of Scots pine (Pinus sylvestris L.) were compressed semi-isostatically according to the CaLignum process in a Quintus press at 25 C and 140 MPa. X-ray computerised tomography images of the same cross-sections were captured before and after compression and compared using a transformation algorithm. In the algorithm the shape of compressed cross-sections were converted to the same shape as non-compressed using the density variation between pixels. Density after compression and the increase in density were analysed using PLS regression. The regressor variables described position in the cross-section and wood properties of each pixel. Heartwood and other resinous wood were less compressed than sapwood, particularly in boards with high resin content. Density also increased little close to the press table, especially in whorls with large knots. Higher original density gives lower degree of compression but still higher density after compression.

  • 24.
    Blomberg, Jonas
    et al.
    Luleå tekniska universitet.
    Persson, Bengt
    Högskolan Dalarna.
    An algorithm for comparing density in CT-images taken before and after compression of Pinus sylvestris2005In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 63, no 1, p. 23-29Article in journal (Refereed)
    Abstract [en]

    Ten plain-sawn boards of Scots pine (Pinus sylvestris L.) were compressed semi-isostatically according to the CaLignum process in a Quintus press at 25°C and 140 MPa. X-ray computerised tomography images of the same cross-sections were captured before and after compression and compared using a transformation algorithm. In the algorithm the shape of compressed cross-sections were converted to the same shape as non-compressed using the density variation between pixels. Density after compression and the increase in density were analysed using PLS regression. The regressor variables described position in the cross-section and wood properties of each pixel. Heartwood and other resinous wood were less compressed than sapwood, particularly in boards with high resin content. Density also increased little close to the press table, especially in whorls with large knots. Higher original density gives lower degree of compression but still higher density after compression. © Springer-Verlag 2005

  • 25.
    Bomark, Peter
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Hirche, Johannes
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Computer Science.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Colour visualisation of real virtual timber using image quilting2015In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 73, no 6, p. 837-839Article in journal (Refereed)
    Abstract [en]

    When presenting images of wood obtained through x-ray computed tomography to an audience inexperienced in interpreting radiological images, explaining the correspondence between mass attenuation and features of wood could be time consuming and confusing. Realistically colourised attenuation images might be a suitable option in order to facilitate understanding of the images. Mass attenuation and colour of wood does not have a simple correlation, so naive grey-scale to colour conversion does not work. This paper describes how image quilting can be used to transfer colour information from a image pair where both mass attenuation and colour is known to a target mass attenuation image. An example of this method applied on scots pine shows that it is capable of retaining the major structures of wood, such as year rings and knots. The method could allow for easier understanding of simulation studies where logs scanned using x-ray computed tomography are virtually sawn.

  • 26.
    Briggert, Andreas
    et al.
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Olsson, Anders
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Oscarsson, Jan
    Linnaeus University, Faculty of Technology, Department of Building Technology.
    Three-dimensional modelling of knots and pith location in Norway spruce boards using tracheid-effect scanning2016In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 74, no 5, p. 725-739Article in journal (Refereed)
    Abstract [en]

    Knots and the orientation of fibres in timber are decisive for the stiffness and strength of boards. Due to large property variations between members, strength grading is necessary. High resolution information of the orientation of fibres, both on surfaces and within members, would enable development of more accurate grading methods than those available today. A step towards three-dimensional (3D) models of the fibre orientation of the entire board volume is the establishment of 3D knot models based on scanning. The light from a dot laser illuminating the surface of a softwood board will, due to the tracheid effect, spread more along the fibres than across resulting in the dot entering an elliptical shape. In this investigation both the shape of the ellipse and the direction of its major axis were used to estimate the 3D fibre orientation on board surfaces. Knot surfaces were identified where the angle between the estimated 3D fibre direction and an approximated direction of the board’s pith exceeded a threshold value. By means of algorithms based on polar coordinates, knot surfaces which belonged to the same physical knot visible on different sides of the board were identified and as a result the position, orientation and volume of each knot were determined. Based on this information, a more accurate position of the board’s pith along the board was calculated. The established models showed good agreement with physical boards. The models constitute a promising starting point for further development of strength grading methods based on tracheid-effect scanning.

  • 27.
    Butylina, Svetlana
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Department of Mechanical Engineering, Lappeenranta University of Technology.
    Hyvärinen, Marko
    Department of Mechanical Engineering, Lappeenranta University of Technology.
    Kärki, Timo
    Department of Mechanical Engineering, Lappeenranta University of Technology.
    Weathering of wood-polypropylene composites containing pigments2012In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 70, no 5, p. 719-726Article in journal (Refereed)
    Abstract [en]

    Outdoor applications of composites have raised questions about their durability. In this study, the effects of outdoor weathering on the properties of wood-polypropylene composites with and without pigments were examined. The composites were placed outdoors for one year, and their colour changes were evaluated after 1, 3, 6, 9 and 12 months of weathering. The durability of the composites was assessed by testing flexural strength and density. Scanning electron microscopy was applied to evaluate the surface degradation of the composites. The weathering resulted in considerable colour fading of the composites. The composites containing darker colour pigments had better colour stability. After weathering, the general trend was a decrease of the flexural strength and density of the composites. The decrease in flexural strength was found to be lower for the composites having higher density.

  • 28.
    Chen, Tingjie
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering. Fujian Agriculture and Forestry University, Fuzhou, China.
    Wu, Zhenzeng
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Niu, Min
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Xie, Yongqun
    Fujian Agriculture and Forestry University, Fuzhou, China.
    Wang, Alice
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Effect of Si-Al Molar Ratio on Microstructure and Mechanical Properties of Ultra-low Density Fiberboard2016In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 74, no 2, p. 151-160Article in journal (Refereed)
    Abstract [en]

    To clarify how the mechanical properties of ultra-low density fiberboards (ULDFs) affected by Si-Al molar ratios, they were prepared with different Si-Al molar ratios. Microstructure and mechanical properties of the ULDFs were tested using scanning electron microscope, energy dispersive spectroscopy, X-ray photoelectron spectrometer, Fourier transform infrared spectrometer, X-ray diffractometer, and microcomputer control electronic universal testing machine. The results showed that Si and Al component were uniformly distributed on the fibers’ surface and the bond of Si-O-C was formed. The different microstructures and relative densities were presented with different Si-Al molar ratios. The results of the modulus of elasticity (MOE), modulus of rupture (MOR) and internal bond strength (IB) were also significantly affected by different Si-Al molar ratios; and their maximum values of 20.78, 0.17, and 0.025MPa were obtained while Si-Al compounds with Si-Al molar ratio of 2:1 was added.

  • 29.
    Cristina, Simón
    et al.
    Technical University of Madrid, Spain.
    Francisco, García Fernández
    Technical University of Madrid, Spain.
    Luis, García Esteban
    Technical University of Madrid, Spain.
    Paloma, de Palacios
    Technical University of Madrid, Spain.
    Hosseinpourpia, Reza
    University of Göttingen, Germany.
    Carsten, Mai
    University of Göttingen, Germany.
    Comparison of the saturated salt and dynamic vapor sorption methods in obtaining the sorption properties of Pinus pinea L.2017In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 75, no 6, p. 919-926Article in journal (Refereed)
    Abstract [en]

    Several methods are available for obtaining the sorption isotherms of wood. Among these, the saturated salt and dynamic vapor sorption methods are the most frequently used  ones. For the first time, the hygroscopic response of wood obtained using these two methods is compared. This is done by determining the 35 and 50°C adsorption isotherms of juvenile and mature wood of Pinus pinea L. The hygroscopic behavior of the two types of wood is different, as the mature wood has a higher moisture content than the juvenile wood in the isotherms studied. Comparison of the static saturated salt method and dynamic vapor sorption shows few significant differences between the equilibrium moisture content obtained by each method during the adsorption process, both in a point by point comparison and in the comparison of quadratic polynomial forms of the Guggenheim Anderson-de Boer model. Moreover, in both methods the point of relative humidity from which multilayer sorption predominates over monolayer sorption is similar.

  • 30.
    Danvind, Jonas
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    PLS prediction as a tool for modeling wood properties2002In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 60, no 2, p. 130-140Article in journal (Refereed)
    Abstract [en]

    During an earlier study, material responses of shrinkage and deformation during air-drying were measured on small wood specimens cut from the cross section of a Pinus radiata log. In this paper the analysis of the collected data and the modeling of studied responses were done using multivariate methods. A first model with all variables and all 104 observations was created. In this model there were observations that deviated from the rest and some of them were therefore excluded from further modeling. Also, weak variables and undesired variables were excluded from further modeling. After these exclusions, 77 observations of wood responses below fiber saturation point remained. The results showed good modeling of radial, tangential and volumetric shrinkage between 0-22% MC, with explained variance (R2) and predicted variance (Q2) at approximately 0.9, and moderate modeling of longitudinal shrinkage, R2 = 0.67 and Q2 = 0.65. It was also shown that longitudinal shrinkage has weak correlation to density-related variables in the studied wood. No model with good predictability of deformation was found. This study showed that PLS prediction modeling of shrinkage and deformation in studied wood samples was found to be an effective and easy-to-use tool for untangling relationships between variables and generating information from data.

  • 31.
    Ebrahimzadeh, PR
    et al.
    Chalmers University of Technology, Department of Polymeric and Textile Materials, S-412 96 Gothenburg, Sweden.
    Kubat, J
    Chalmers University of Technology, Department of Polymeric and Textile Materials, S-412 96 Gothenburg, Sweden.
    McQueen, DH
    Chalmers Innovation Center, Chalmers University of Technology, S-412 96 Gothenburg, Sweden.
    Dynamic mechanical characterization of mechanosorptive effects in wood and paper1996In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 54, no 4, p. 263-271Article in journal (Refereed)
    Abstract [en]

    Dynamic mechanical studies in dual cantilever and tensile stretching mode of Scots pine veneer, birch veneer and paper under stepwise humidity changes between 5% and 85% relative humidity are reported. The loss tangent (tan delta) shows a transient peak every time the relative humidity of the surrounding atmosphere is changed. In the bending mode a clamping arrangement that is freely movable in the longitudinal direction gives more distinct damping peaks than does a static fixture.

    There is a close relationship between the rate of sorption/desorption and the shape of the tan delta peak. In response to reduction of the rate of humidity change the damping transients slowly disappear. They also diminish in strength as the temperature is raised toward 60 degrees C. Their strengths increase as the measuring frequency is lowered toward 0.01 Hz. Also, when the samples are highly compressed or prestressed with static loads the peak heights are greatly reduced. The tans peaks become less distinct and eventually disappear when the amplitude of the vibration increases. Long time testing results in significant changes in the shapes of the tan delta versus time data.

    A working hypothesis is that these phenomena are closely related to molecular diffusion of water through the sample material. Simple estimates show that the relaxation time for a diffusion related process should be of the order of a minute.

  • 32.
    Ekevad, Mats
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Cristovao, Luis
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grönlund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Öhman, Micael
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Geometry of kerf when curve sawing with a circular rip-saw2014In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 72, no 6, p. 809-814Article in journal (Refereed)
    Abstract [en]

    Rip-sawing following the curvature of a crooked log means advantages for yield. However, the possibility to saw in a narrow curve with a circular saw blade is limited because of the inherently flat geometry of circular saw blades. For a double arbour circular saw the situation is even more problematic because the two blades have a certain overlap and thus, the two arbours are not positioned in the same horizontal position. In this study, a theoretical geometrical study of the creation of a kerf with a single circular saw blade and with a double arbour circular saw with two saw blades was examined. Results for stiff saw blades show that the kerfs become in general curved and inclined (tilted) in the vertical direction and also that the width of the kerfs for double arbour saws becomes wider at the top and bottom of the cant than in the middle. Additionally, the sawn boards obtain varying thickness along their width because of the varying kerf width. A comparison with experimental thickness data from four test sawings at a sawmill indicates that the theoretical results are valid and that curve sawn boards become thinner than straight sawn boards.

  • 33.
    Eklund, Urban
    Luleå tekniska universitet.
    Influencing factors on sawing accuracy in a bandsawmill2000In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 58, no 1-2, p. 102-106Article in journal (Refereed)
    Abstract [en]

    The influence of the cutting height, the feed speed, the strain in the band and the cutting time for the band on the sawing accuracy has been investigated by fractional factorial analysis in a normal production situation at a sawmill in Sweden. Factorial analysis has proven to be a useful method when checking the situation at a sawmill as there are many factors that influence the sawing results. The findings in this investigation are: (a) the feed speed must be adapted to the actual cutting height to a higher degree than done today; (b) the working time for the band has some influence on the result but not to the great extent as expected; (c) the feeding equipment has probably a big influence on the sawing accuracy

  • 34. Epmeier, Hannah
    et al.
    Johansson, Marie
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design. Byggteknik.
    Kliger, Robert
    Westin, Mats
    Bending creep performance of modified timber2007In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 65, no 5Article in journal (Refereed)
    Abstract [sv]

    The present study is a supplement to Epmeier and Kliger (2005), which investigated the effect of three different modification methods (acetylation, modification with methylated melamine resin and heat treatment in vegetable oil) on four material properties (density, modulus of elasticity (MOE), creep deflection and relative creep) and their inter-relations. In this study, another modification method (furfurylation) and four additional material parameters (“relative stiffness”, i.e. MOE/density, moisture content, change in moisture content and anti-creep efficiency) and their correlations are included. In addition, the creep curves were analysed to assess the development of bending creep performance. The properties were assessed by experimental work on 132 specimens of Scots pine sapwood with dimensions of 45×70×1100 mm3. It was found that modification leads to significant changes in material properties. Furfurylation increases density and reduces creep deflection, relative creep and moisture content. Modified timber tends to deflect and creep significantly less than untreated timber. However, the extent of reduction in relative creep appears not to be related to the extent of reduction in creep deflection. Initial deflection and/or modulus of elasticity are suitable for predicting the creep deflection of untreated and modified timber.

  • 35.
    Eriksson, John
    et al.
    Chalmers University of Technology.
    Ormarsson, Sigurdur
    Chalmers University of Technology.
    Petersson, Hans
    Växjö University, Faculty of Mathematics/Science/Technology, School of Technology and Design.
    An experimental and numerical study of the shape stability in glued columns2005In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 63, no 6, p. 423-429Article in journal (Refereed)
    Abstract [en]

    The study concerns the question of how the shape stability features of laminated columns of Norway spruce can be improved in terms of twist through optimal orientation of the individual laminates. Both experimental testing and numerical simulations were employed for evaluating twist stability. In all the columns studied, deformations were measured experimentally at different moisture content levels. A number of columns were also selected for numerical analysis in order to obtain a more thorough understanding of the twist behavior involved, their geometries and material properties of interest being determined. The experimental results showed the twist stability of the columns to be highly dependant upon the internal orientation of the individual laminates. It was also found that high quality columns in terms of shape stability could be manufactured, even when the center-core material has a strong twist tendency. The numerical simulations performed were in close agreement with the experimental results.

  • 36.
    Eriksson, John
    et al.
    Chalmers University of Technology.
    Ormarsson, Sigurdur
    Chalmers University of Technology.
    Petersson, Hans
    Chalmers University of Technology.
    Experimental study of shape stability in glued boards2004In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 62, no 3, p. 225-232Article in journal (Refereed)
    Abstract [en]

    An experimental study of shape stability in wooden glued boards was performed to verify certain results of particular interest obtained earlier in numerical simulations. Possibilities for achieving products of good shape stability by gluing boards together in an optimal way are discussed. Since twist is often the most serious form of distortion defects for the user, it was the main type of board deformation considered. Three types of glued products were tested. The experiments show clearly that glued boards can be produced that remain stable in shape when exposed to extreme variations in moisture. The results agree well with the numerical simulations performed earlier. It was found that initial twist could be reduced by proper application of pressure during gluing and that through gluing the occurrence of cracking defects on visible surfaces could be substantially reduced.

  • 37.
    Fredriksson, Magnus
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Berglund, Anders
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Validating a crosscutting simulation program based on computed tomography scanning of logs2015In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 73, no 2, p. 143-150Article in journal (Refereed)
    Abstract [en]

    Wood scanners and software for calculating crosscutting positions have been used in the wood industry for some years now. The scanners are used to detect biological and geometrical deviations on the sawn timber, which makes it possible to remove undesired defects using crosscut saws. Yield calculations for crosscutting have not been investigated to the same extent as sawing yield calculations for primary breakdown of logs, especially if the whole chain from log to end product is considered. The objective of this study was to validate the result of a computer program developed for simulating crosscutting of boards. The crosscut simulations were performed with respect to knot characteristics on Scots pine (Pinus sylvestris L.) board surfaces. Validating a crosscutting simulation program would mean that it can be used to investigate how raw material and customization of quality rules affect the yield in a wood production chain from log to crosscut end product. The validation showed that crosscutting yield for boards could be predicted with a root mean square error of 13 percentage points, and the technique can be used to identify unsuitable logs for a certain product at an early stage of production.

  • 38.
    Granström, Karin
    Karlstad University, Faculty of Technology and Science, Department of Energy, Environmental and Building Technology.
    Emissions of sesquiterpenes from spruce sawdust during drying2009In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 67, no 3, p. 343-350Article in journal (Refereed)
  • 39. Grundberg, Stig
    et al.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Measuring active wood fracture surfaces1993In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 51, no 1, p. 49-54Article in journal (Refereed)
    Abstract [en]

    This report describes a measurement method, based on image processing, for calculating the proportion of active wood fractures in a sheet of particle board that has been pulled apart. This method gives an indirect measurement of the effectiveness of the glue in a particle board. The basic procedure is to separate different surfaces on both sides of the tensile fracture. The separation of the glue covered surfaces from wood surfaces has been enhanced by a development process. The separated surfaces for each side, represented in the form of a binary image, are added, and a proportion of the surface with coinciding wood surfaces represents the proportion of wood fractures. The error analysis covers the randomly obtained coinciding surfaces.

  • 40. Grönlund, Ulla
    Quality variations in the chain log-board-blank1994In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 52, no 1, p. 57-62Article in journal (Refereed)
    Abstract [en]

    To achieve a high economic yield in the wood industry it is important to control the grading procedures and to know the quality distribution in different steps. Scots pine (Pinus sylvestris) timber from Sweden has been compared regarding quality variations in the chain log-board-blank caused by biological properties and subjective grading procedures. This study describes the quality distributions in the treatment of trees from harvesting throughout sawing and to the user's judgements, the correlation between the grading procedures in various steps, and the yield in all classes based upon the customer's opinion. The results emphasise that current classification system is very hazardous and seems not be in concordance with the customers' demand. The subjective and visual grading procedures are not sufficiently effective to predict the properties. Three main needs must be satisfied in order to reduce the costs for poor quality; knowledge about the biological variations, new equipment for grading and knowledge about the customers' needs and behaviours

  • 41. Grönlund, Ulla
    et al.
    Broman, Olof
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Relations between wood properties and manual grading: an approach based on multivariate analysis1995In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 53, no 6, p. 413-420Article in journal (Refereed)
    Abstract [en]

    Pinus sylvestris ) boards from Sweden have been scanned on all four sides. The output variables together with additional variables describing e.g. geographic areas and manual classification class are analysed by using multivariate statistical methods. The purpose was to study if the manual grading procedure of boards/blanks are in conformity with automatically measured properties and if there is any single property that carries more information than others. The results show that most of the original variables are uncorrelated and therefore it is impossible to reduce and simplify the grading procedure by e.g. measuring only a few characteristics. The study also shows the weakness of the objective grading procedure describing only the amount of characteristics.

  • 42.
    Gustafsson, Stig-Inge
    Linköping University, Department of Mechanical Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Finite element modelling versus reality for birch chairs1996In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 54, no 5, p. 355-359Article in journal (Refereed)
    Abstract [en]

    When chairs and other furniture are designed the work is mostly founded on handicraft experience. Calculations based on solid mechanics theory are almost never used in order to find out optimal solutions for different wood members, or the structure as a whole. We have therefore studied a simple chair, made of birch, where the emphasis is laid on its ability to carry different loads. Using the method of finite elements we have predicted the strain and stress at different points on the chair structure. Further, we have manufactured the chair and exposed it to the same load pattern as used in the finite element calculations. The strain has been monitored and compared to the calculated value at the points of most interest. The result shows that part of the calculations corresponded fairly well with the monitored values but also that much work still remains in order to totally predict the accurate structural behaviour for such a simple frame as a chair. Probably, some of the discrepancies depend on the wood material which exhibits so different response for stress in different directions.

     

  • 43.
    Gustafsson, Stig-Inge
    Linköping University, Department of Management and Engineering.
    Furniture design by use of the finite element method1995In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 53, p. 257-260Article in journal (Refereed)
  • 44.
    Gustafsson, Stig-Inge
    Linköping University, Department of Mechanical Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Indetermined chair frames of ash wood1997In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 55, no 2-4, p. 255-259Article in journal (Refereed)
    Abstract [en]

    During recent years more interest has been emphasised on wood as a construction material. This is so because wood is a renewable resource and also because problems with waste do not emerge when the wooden structure is taken out of operation. On the contrary this waste is still a resource even if the structure is demolished. Wood could always be used as a biomass fuel which is not expected to contribute to the greenhouse effect. In Sweden most of the interest has been emphasised on our conifers while broad leaved species are much less examined. This paper shows the result from the Finite Element Method applied on indetermined chair frames and compares these findings with actual testing in our laboratory. The conclusion is that there are considerable discrepancies between calculations and real behaviour even for relatively simple structures such as a chair frame. It seems that the real chair is stronger than expected even if the joints between the furniture members must reduce the overall strength found by the FEM calculations.

  • 45.
    Gustafsson, Stig-Inge
    Linköping University, Department of Mechanical Engineering, Energy Systems. Linköping University, The Institute of Technology.
    Solid mechanics for ash wood1999In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 57, no 5, p. 373-377Article in journal (Refereed)
    Abstract [en]

    Wood is an anisotropic material and, further, because of its natural origin the mechanical properties might significantly differ also between each of the samples tested. Ordinary methods for evaluation of solid mechanic properties often destroy the tested specimens. It is therefore not common practice to evaluate more than one property, e.g. Young's modulus for tension, at the same time using the same sample. Different tests also have different recommendations of how the test specimens should be designed in order to test the property of interest. When calculations are to be made by e.g. the Finite Element Method values for a number of properties must be included and when the resulting construction is examined after this, it is not easy to decide if discrepancies depend on unreliable input data. This paper therefore describes tension, compression and bending tests for one specific detail, namely a wood beam of ash wood. The applied forces are well under those where rupture occurs and hence the material is assumed to be intact during all testing procedures.

  • 46.
    Hagman, Olle
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Multivariate prediction of wood surface features using an imaging spectrograph1997In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 55, no 6, p. 377-382Article in journal (Refereed)
    Abstract [en]

    Picea abies , Pinus sylvestris), is reported, showing verified 92-94% correct classification. It is shown that compression wood classification could be reduced to an uncomplicated linear model using just a few spectral components where the most important one is around the limit for visible light going to the Ultraviolet spectra. This almost univariate behaviour for the model is not the common behaviour for other wood surface features

  • 47.
    Hagman, Olle
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Wood Science and Engineering.
    Grundberg, S.A.
    Swedish Institute for Wood Technology Research.
    Classification of scots pine ( Pinus sylvestris ) knots in density images from CT scanned logs1995In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 53, no 1, p. 75-81Article in journal (Refereed)
    Abstract [en]

    This study was carried out to test methods for separating knots from clearwood in a digital image stack when scanning for internal defects with a medical CT-scanner. Scots pine knots, represented by its tangential surface density image extracted from a CT-image stack, have been classified by two different methods showing equal results. The knots are classified in four knot types by an Artificial Back-propagation Neural Network (ANN) and a Partial Least Squares Modelling with Latent Variables (PLS) model. The classification precision of aim of four different knot types, is between 85% and 97%. The results indicate that both methods may be useful tools in order to describe and classify knots in concentric surfaces around the pith in CT-images and thereby extract parametrical models from CT raw data image stacks. A simplified classification model has been obtained, by analysing the learning patterns in both the ANN and PLS model, that classify knots and transform density related data to segmented and classified parametrical descriptions.

  • 48.
    Hameed, Mahmood
    et al.
    University of Göttingen, Germany.
    Behn, Claus
    University of Göttingen, Germany.
    Roffael, Edmone
    University of Göttingen, Germany.
    Dix, Brigitta
    Wilhelm-Klauditz-Institut (WKI), Germany.
    Benetzbarkeit von Recyclingspänen und ,,frischen“ Holzspänen mit verschiedenen Bindemitteln: [Wettability of fresh chips (chips obtained directly from wood) and chips obtained by mechanical disintegration (M-chips) and  thermohydrolytical degredation (T-chips) of particleboards with UF-, PF-resins and binders based on PMDI (polymers of diphenylmethan diisocyanates)]2005In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 63, no 5, p. 394-395Article in journal (Refereed)
    Abstract [de]

    Nach allen Messzeiten zeigten die „frischen“ Holzspäne eine bessere Benetzung mit UF-Harz, PF-Harz und PMDI-Klebstoff als die Recyclingspäne. Besonders durch mechanische Zerklei- nerung gewonnene Recyclingspäne weisen eine geringere Benet- zung auf als die „frischen“ Holzspäne. Dies ist womöglich auf das den Recyclingspänen anhaftende Binde- und Hydrophopie- rungsmittel zurückzuführen. Die bessere  Benetzung der durch thermohydrolytischen Aufschluss gewonnenen Späne ist möglicherweise darauf zurückzuführen, dass während des Aufschlus- ses Teile des Bindemittels chemisch abgebaut und wasserlöslich werden. Die Benetzung der Recyclingspäne mit PMDI ist auffallend besser als mit UF- und PF-Harz. Dies ist unabhängig davon, ob die zu benetzenden Späne durch mechanische Zerkleinerung oder durch thermohydrolytischen Aufschluss gewonnen wurden.

  • 49.
    Hameed, Mahmood
    et al.
    Göttingen University, Germany.
    Behn, Claus
    Göttingen University, Germany.
    Roffael, Edmone
    Göttingen University, Germany.
    Dix, Brigitta
    Wilhelm-Klauditz-Institut (WKI), Germany.
    Wasserrückhaltevermögen von Recyclingspänen und von direkt aus Holz gewonnenen Spänen: [The water retention value of dried wood particle (obtained directly from wood) was determinated and compared with that of particle obtained by mechanical disintegration (M) or thermohydrolytical degredation (T-) of UF-bonded particleboards]2005In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 63, no 5, p. 390-391Article in journal (Refereed)
    Abstract [de]

    Das Wasserrückhaltevermögen nimmt mit Verlängerung der Lagerungsdauer im Wasser zu, wobei die Zunahme im Falle der mechanisch gewonnenen Recyclingspäne (M) besonders ausge- prägt und im Falle der thermohydrolytisch gewonnenen Späne (T) auffallend gering war. Gegenüber den direkt aus Holz gewonnenen Spänen weisen die mechanisch gewonnenen (M) besonders niedrige WRV-Werte auf. Durch die thermohydrolytische Behandlung der Späne, bei der erhebliche Teile des Bindemittels abgebaut werden, nimmtdas  Wasserrückhaltevermögen  deutlich  zu  und  erreicht  sogar Werte,  die  höher  liegen  als  die  von  „frischen“  Spänen.  Für den Abbau des UF-Harzes infolge der thermischen Behandlung spricht auch der gegenüber den mechanisch gewonnenen Spänen (M) niedrigere Stickstoffgehalt der thermohydrolytisch erzeug- ten Späne (T). Es ist nicht auszuschließen, dass während der ther- mohydrolytischen Behandlung ebenfalls Acetylgruppen im Holz abgespalten werden, die zu einer zunehmenden Hydrophilie der Späne führen. Auf einen Abbau von Acetylgruppen deutet der vergleichsweise hohe Gehalt an Essigsäure in den Kaltwasserex- trakten der Späne hin, der nach der Thermohydrolyse festgestellt wurde.

     

  • 50.
    Hameed, Mahmood
    et al.
    Georg-August-Universität Göttingen, Germany.
    Roffael, Edmone
    Georg-August-Universität Göttingen, Germany.
    Eindringtiefe verschiedener Bindemittel in Splintholz- und Kernholzspänen der Kiefer (Pinus sylvestris L.): [On the penetrability of various glues from sap- and heartwood of Pine (Pinus sylvesteis L.)]2001In: European Journal of Wood and Wood Products, ISSN 0018-3768, E-ISSN 1436-736X, Vol. 58, no 6, p. 432-436Article in journal (Refereed)
    Abstract [en]

    Investigation of the penetrability of various glues [urea-formaldehyde resin (UP-resin), phenol-formaldehyde resin (PP-resin), melamine-urea-phenol-formaldehyde made of pine sapwood and heartwood revealed: the various glues penetrate chips from pine sapwood regardless of tree age, height of the sample studied and surface structure deeper than in those made of heartwood. The various glues more deeply penetrate chips from sapwood and heartwood of the 48-year-old pine than chips from sapwood and heartwood of the 124-year-old pine. The penetrability of various glues in chips from sapwood and heartwood of the 124-year-old pine increases with increasing height of the sample studied. Moreover,  glues penetrate sanded surfaces of chips from sapwood and heartwood of the 48- und the 124-year-old pine to a lesser extent than unsanded chip surfaces.

123 1 - 50 of 139
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